Differential hoist



Patented Aug. 28, 1934 I UNITED i smeg? 3 Claims.

It is well known to those skilled in the art that in this type of hoist, where two sheaves of different diameters are employed, friction in the parts is depended upon to sustain the load and 5 prevent the same from getting out of control when,` being lowered. This friction, however, greatly decreases the efficiency of the hoist and it has been an object of my invention to provide a hoist in which there shall be just enough friction to balance the difference in the turning movements of the two sheaves, my device being so designed so as to relieve the friction when the load is being lifted.

Another object has been to provide simple and I6` inexpensive means for connecting and disconnecting the anti-friction means of the hoist.

Another object has been to provide a device of this nature having comparatively few parts and not likely to get out of order.

The above objects and advantages have been accomplished by the device shown in the accompanying drawing, of which:

Fig. 1 shows a vertical, sectional view, taken through my differential hoist.

Fig. 2 is an enlarged, sectional view of parts of the lower hoist block and is taken on line 2-2 of Fig. 1.

Fig. 3 is a similar view and is taken on line 3--3 of Fig. 1.

My device comprises an upper hoist block 10 and a lower hoist block 11. The upper hoist block has the customary yoke 12 which carries at its upper end a swivel hoist hook 13 and at its lower bifurcated end a shaft 14. Mounted upon 35 the shaft 14 is the` upper double sheave 15 which has grooves 16 and 17 formed therein of different diameters. The shaft 14 is held in place by suitable cotter pins 18 and suitable roller bearings 19 are mounted within the hub 20 of the 40 sheave 15 for reducing the friction of this sheave.

The lower hoist block 11 comprises a yoke 25 having at its lower end the usual swivel hook 26. In the upper bifurcated end of this yoke 45 -is rotatably mounted the lower shaft 27. This shaft is held in place by means of cotter pins 28. Upon this shaft is mounted the lower sheave 29. A suitable anti-friction bearing is provided `between the hub 30 ofthe lower sheave and the ofshaft 27 which may be in theform of rollers 31. These rollers are retained in place by means of a washer 32. A portion of the hub 30 has bearing contact with the shaft 27 and opposite uthis portion the shaft is provided with a series 5510i ratchet shaped notches 33. Carried by an extension 34. of the hub 30 of this sheave is a plunger pawl having its forward end 36 shaped to engage the notches 33 in the shaft.

A spring 37 is arranged in the recess 33 of the hub extension .34, and serves to keep the pawl 605 35 pressed against the shaft. Obviously, the chainV 4G, shown diagrammatically by the dot and dash line, is reeved around the grooves 16 and 17 of the upper double sheave l5 and around the lower sheave 26, the direction of such reev- 35 ing being such that the lower sheave will be rotated in a clockwise direction, as viewed in Fig.

2, when the load is being lifted. During such rotation, the plunger pawl 35 will ride over the notches 33, and the lower sheave will be sup- 701-' ported by the roller bearings. When the load is being lowered, obviously, the lower sheave will be rotated in the opposite direction and during such rotation the plunger pawl 35 will engage one of the notches 33 and thus connect the 75" sheave 29 with its shaft 27 and cause the shaft to be rotated in the supports of the bifurcated end of the lower sheave yoke 25. Suiiicient friction will thus be created to permit the load to be sustained, if desired, and to permit it to be easily lowered without the possibility of its getting out of control.

From the foregoing, it will be obvious that the application of my invention to a differential hoist does not complicate the hoist or materially 35 change its design, but does accomplish the deslred results by means of few and inexpensive parts conveniently arranged in such manner that a very durable and inexpensive hoist is produced. Y

Obviously, some modifications of the details herein shown and described may be made without departing from the spirit of my invention or the scope of the appended claims, and I do not, therefore, wish to be limited to the exact embodiment herein shown and described, the form shown being merely a preferred embodiment thereof.

Having thus ldescribed my invention, what 1 claim is: 1w

1. A differential hoist comprising an upper hoist block having a double sheave, a lower hoist block having a single sheave, and means carried by the hub of the sheave of the lower block and directly engageablewith the shaft of said sheave during the lowering operation of the hoist; whereby both shaft and sheave are rotated in unison.

2. A hoisting device comprising an upper hoist block having a double sheave, a lower hoist. nd

lower block for rotatably supporting the sheave, anti-friction means between the lower sheave and the shaft thereof, said shaft being formed in its periphery with a plurality of notches, and a spring-pressed plunger pawl carried by the hub of the lower sheave and engageable with the notches of the shaft to lock the sheave upon the shaft when the load supported by the hoist is being lowered.

FRANK E. STAHL. 

